1. Field of the Invention
The present invention relates generally to pollution prevention and, more particularly, to a bulk liquid cargo spill prevention system of the expandable bladder bladder type for a bulk liquid cargo tanker.
2. Description of the Related Art
In the related art, methods and systems for preventing or controlling the spillage of bulk liquid cargoes such as oil into the sea are well known. In fact, there are many tanker ships whereby the loss of liquid bulk cargoes, usually petroleum products, is attempted to be minimized in case of cargo tank rupture through the ship's design. The most recent and well know is the addition of a second hull to a tanker vessel whereby the outer hull protects the inner hull/cargo tank from rupture. There are also tankers designed with the cargo tanks located relative to the waterline in such a fashion that in the event of a tank rupture, the oil leaking out of the tank is minimized by a phenomena known as hydrostatic lock. There are also tankers with various arrangement of cargo tanks, ballast tanks and piping systems for transferring liquid bulk cargo to the ballast tank in the event of cargo tank rupture.
Each of these methods and designs has its limitations. The double hull tanker significantly increases ship construction costs and seriously affects the ship's stability. Other ship designs employing gravity means or pumps to move liquid bulk cargo to an empty ballast tank generally do so at the expense of decreasing ship stability. Another design provides limited impact protection of a cargo tank by surrounding the tank with a single flexible bladder which deflect and yield to the energy of impact. Similarly, yet another design consists of a protective layer placed against the hull segregated from the liquid cargo by a flexible liner. If the hull is punctured, the protective layer will hold the flexible liner in place and hence the liquid cargo will be prevented from leaking from the tank.
There exist in the art other methods and devices that aren't an integral part of the ship's design but can be employed in the event a liquid bulk cargo tank is ruptured. One design contemplates pumping liquid cargo into a collapsible bladder which is placed over the ship's side into the sea and made buoyant. The bladder is normally stowed in a collapsed configuration on deck ready for immediate deployment. Another design contemplates a collapsible bladder normally stowed within a cargo tank that the liquid cargo can be pumped into in the event the tank is ruptured. The bladder is designed to conform to the interior contour of the cargo tank and as the liquid cargo pumped into the bladder causes the bladder to expand the interior volume of the tank is encapsulated. The outer wall of the bladder then forms a seal on the ruptured wall of the tank preventing any further flow of seawater into the tank. There is no further discharge of liquid cargo since all of the liquid cargo in the tank has been pumped into the bladder.
The present invention is of the collapsible bladder type stowed in the cargo tank with a novel collapsible bladder arrangement and control system.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention; however, the following references were considered related:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 4,389,959 Conway June 28, 1983 5,052,319 Beyrouty October 1, 1991 5,347,943 Fujita, et al. Sep. 20, 1994 5,353,728 Strange Oct. 11, 1994 5,271,350 Newburger Dec. 21, 1993 5,349,914 Lapo, et al. Sep. 27, 1994 5,735,227 Goulding April 7, 1998 3,844,239 McLaughlin et al. Oct. 29, 1974 3,906,880 Hebert Sep. 23, 1975 5,119,749 Velleca, et al. June 9, 1972 5,125,353 McGuiness June 30, 1992 ______________________________________
The above list of patents can be divided into two groups. The first group of patents are considered related to but not directly relevant to the present invention and require no further discussion:
U.S. Pat. No. 4,389,959 issued to Conway discloses an improved tanker vessel of the type where the liquid cargo tanks are arranged in such a fashion that should the hull be breached the liquid cargo is prevented from leaking from the hull through hydrostatic loading;
U.S. Pat. No. 5,052,319 issued to Beyrouty discloses a collapsible bladder which can stored on deck but deployed over the side to pump liquid cargo from a ruptured leaking cargo tank;
U.S. Pat. No. issued to Fujita et al., discloses another tanker design where the hull is of a double layer design where the outer layer is supposed to protect the inner layer, serving also as the outerwall of a liquid cargo tank, from further damage. In addition, the liquid cargo tanks are arranged in such a fashion that should the hull be breached the liquid cargo is prevented from leaking from the hull through hydrostatic loading;
U.S. Pat. No. 5,353,728 issued to Strange discloses an improved tanker design where a passive, gravity-responsive, fluid transfer system provides very rapid fluid communication between selected cargo tanks and adjoining ballast tanks;
U.S. Pat. No. 5,271,350 issued to Newburger discloses an apparatus comprised of a series of bladder modules whose walls are made of a flexible material of sufficient strength to substantially withstand rupture upon such impact. Each flexible module comprises an inboard cargo-carrying bladder surrounded out-boardedly by a buffer bladder containing air under pressure;
U.S. Pat. No. 5,349,914 issued Lapo, et al., discloses a device for impeding the spillage of a liquid cargo which consists of a protective layer placed against the inner surface of the hull and a flexible inner layer placed between the protective layer and the liquid cargo, so that if the hull is punctured, the protective layer will hold the flexible liner and the liquid cargo in place;
U.S. Pat. No. 5,735,227 issued to Goulding discloses an apparatus for sealing a rupture in a wall comprised of a backing plate and a seal. The '227 reference teaches that such an apparatus may be used to seal a ruptured hull of a ship.
The second group of patents from the list above are considered relevant and directly related to the present invention:
U.S. Pat. No. 3,844,239 issued to McLaughlin et al. discloses a liquid carrying tanker with an impermeable, elastomeric tailored lining releasably fixed to the inner walls of the liquid cargo tank, the lining being adapted to separate from the walls of the tank when the tanks are impacted such as when the ship is in a collision or grounded. The distortion of the liner causes the liquid pressure in the liner to increase and force the liquid from the liner into another tank;
U.S. Pat. No. 3,906,880 issued to Hebert discloses a vinyl liner manufactured to fit within and conform to the interior of a liquid cargo carrying tank. Said liner is fixed to the top of the tank and designed to be dropped into the tank and have the liquid cargo from the tank pumped into when the tank is ruptured;
U.S. Pat. No. 5,119,749 issued to Velleca, et al. discloses another system whereby liquid from a ruptured cargo tank is to be pumped into a flexible liner located within the tank for rapid deployment. The expanded liner holding the liquid cargo prevents it from leaking through the hull and at the same time seals the ruptured hull preventing seawater from further entering the hull;
U.S. Pat. No. 5,125,353 issued to McGuiness discloses yet another system whereby liquid from a ruptured cargo tank is to be pumped into a flexible liner. The expanded liner holding the liquid cargo prevents it from leaking through the hull and at the same time seals the ruptured hull preventing seawater from further entering the hull. However, the '353 reference indicates that this system is not fixedly connected to the interior of a cargo tank but is to be dropped through a hatch in the top of the tank when needed.
With the exception of the '353 reference, all of the inventions in the second group are like the present invention in that they all have a flexible, collapsible liner or bladder which is fixedly connected to the interior of a cargo tank for rapid deployment should one of the tank walls be breached. Once the tank wall is breached, a pumping means pumps the liquid cargo into the bladder causing it to expand. The liner or bladder was manufactured to conform to the interior of the tank so that any obstacles in the tank would not impede the expansion of the tank and so that the entire volume of liquid can be pumped into the bladder. The expanded bladder also serves to form a seal against the inner wall of the tank which was ruptured preventing any further spillage of seawater into the tank.
What is different about the present invention from the these inventions is a novel means whereby the collapsible bladder is fixedly connected to an interior sidewall of the tank and deployed suspended hanging from a track via a tram and trolley assembly. Suspending the bladder from the track in this manner not only guarantees the successful deployment of said bladder but also allows the bladder to be retracted and collapsed back correctly when the tank rupture has been fixed. A novel means for sensing when a tank is ruptured and signaling when to deploy the bladder is also disclosed using an advanced fiber optics sensing system. In addition, a pumping means integrated into the design of the ship and the cargo tanks is disclosed with a self-actuating emergency backup system being further provided. None of the aforementioned prior art discloses any type of control system for use with such a emergency bladder system or a means for sensing when to employ said system as in the present invention.
Consequently, a need has been felt for providing an apparatus for containing liquid cargo when a cargo tank is ruptured which can be deployed rapidly, automatically, is retractable and reuseable, and provides an emergency backup means should power from the tanker be unavailable. The present invention fulfills this need.